Centered Square Thumbnail Image in Asp.net - How can I do this?

When users upload a gif or jpg, one of the thumbnails I want to create is a square 70x70 thumbnail. So if the image is not already square, I will have to somehow center the image, resize the height or width (depending on which one is the smallest), and then crop the top and bottom to make the square thumbnail. Anyone know how to do this, or know of a control that can do this?

Thanks.